The present invention relates to certain spinel-containing refractory mixes and resultant shapes, particularly brick suitable for use in rotary lime and cement kilns.
U.S. Pat. No. 5,021,364 describes the efforts to replace magnesite-chrome refractory shapes with other material including magnesite-spinel brick. This patent discloses that improved thermal spalling resistance can be obtained, particularly in kilns with lime-rich clinkers, when one utilizes a purified magnesia-alumina spinel grain and utilizes a dead-burned (sintered) magnesite therewith.
Such magnesite spinel brick, while having found general acceptance throughout the rotary cement kiln industry as a chrome-free alternative to magnesitechrome brick, have relatively low strength at temperatures greater than 2500.degree. F. which may impart a limitation on the service performance of these brick. Moreover, in some current cement kilns magnesite-spinel brick are finding difficulty because these kilns are fired with liquid, hazardous waste fuels. Such fuels are high in chloride and sulfur and the present magnesite-spinel brick do not have a sufficiently high corrosion resistance to such fuels and thus they lack the desired service performance.